Loudspeakers – Consist of a circular permanent magnet surrounding a freely moving coil. The coil is attached to a cone-shaped, flexible diaphragm or speaker cone. – When current passes through the coil, magnetic forces act on the coil, causing it to move in or out depending on the direction of the current. – If AC current passes through the coil, it will move alternatively in and out as the current changes direction. The coil will therefore vibrate at the same frequency as AC current.
Society has become increasingly dependant on electricity over the last 200 years 1. 1 & 1. 2 – Wood was firstly used as an energy source, the chemical energy in it was converted into heat energy to produce fire. The fire was used for heating, cooking and as a means of defense. – Domesticated animals were then used as an energy source, they were a source of mechanical energy, more food could be produced, towns developed and populations increased.
– Wind and Water was used next as a source of mechanical energy, this expanded trading and more efficient production of food from grain. – Coal became the main fuel in the 19 th century as a result of dwindling supplies of wood and the superior energy content of coal. Increased use in coal led to the development of the steam engine to pump water from coal mines. – Coal gas was produced by heating coal in absence of air, used for street lighting and a source of heat and light in houses. This led to greater social activity during the night.
It warms and cools our homes, cooks our food, plays our music, and gives us pictures on television. Energy is defined as the ability or the capacity to do work. We use energy to do work and make all movements. When we eat, our bodies transform the food into energy to do work. When we run or walk or do some work, we ‘burn’ energy in our bodies. Cars, planes, trolleys, boats, and machinery also ...
1. 3 – Some remote locations cannot be connected to a power station. – Such places frequently use small generators in which a coil is rotated by internal combustion engine using petrol or oil. – Array’s of solar cells, which convert the energy of sunlight into electrical energy, and small wind gener taros are also sued for some specialised purposes. Galvani and Volta – In 1780, Luigi Galvani undertook a series of experiments designed to examine the effects of static electricity on the nerves and muscles of frogs. – He noticed that the legs of a directed frog twitch when their spinal cords are connected to an iron nail by a brass hook.
– Galvani took these observations to confirm the existence in animals of an electrical fluid and the so called animal electricity. – Alessandro Volta was a friend of Galvani and corresponded with him on the nature of electricity. – Volta questioned Galvani’s assumption that ‘animal electricity’ caused a frogs legs to twitch. Instead, he hypothesized that the electric current that was produced came as a result of contact between the moist tissue and the two different metals. – In 1794, using just metals and moisture, Volta was able to produce an electric current refuting Galvani’s claim that it had to do with life.
This generated the debate between Galvani and Volta and their respected followers. – In 1800, using a pile of alternating discs of copper and zin separated by paper soaked in brine (salt water), Volta produced the fire ‘battery’ or voltaic pile. This invention effectively silenced Galvani and was a major forerunner for the modern day battery. 2. One of the main advantages of electricity is that it can be moved with comparative ease from one place to another through electric circuits 2. 1 – refer to 50 to 53 in excel and 94 to 96 in jacaranda 2.
2 – The SI unit of charge is one Coulomb (C).
One coulomb is equivalent to the charge of 6. 25 10 (18) C – The charge on one electron is -1. 6 10 (-19) C and the charge on one proton is +1. 6 10 (-19) C 2. 3 – As a force of magnitude F acts on a charge, q, placed in an electric field, then the magnitude of the electric field strenght, E, is given by the formula: E = F / q – The direction of the electric field strenght is the direction of the force that acts on a positive charge placed in the field.
Dot Point: "h Identify data sources, gather, process and analyze secondary information about differing views of Volta and Galvani about animal and chemical electricity, and discuss whether their different views contributed to increased understanding of electricity. Research Topic! V Outline the debate between Galvani and Volta concerning the nature of electricity. To learn of the controversy ...
– The AC current that passes through the coil of a loudspeaker is derived from sound waves that have been converted into AC currents by a microphone. – The vibrations of the coil cause the diaphragm to vibrate and generate sound waves that reproduce the sound waves from the original sound.